Means for tuning electrical oscillators



June 4,19 6 N. R. BLIGH ET AL vMEANS FOR TUNING ELECTRICAL OSCILLATORS Filed Dec. 23, 1945 2 Sheets-Sheet l INVENTO RS NORMAN RICHARD BLIGH DOUGLAS MAX HELLER LUIS CHARLES STENNING ALEXANDER ALBERT CHUBB 737 5 AT TO R N EY n 4,1946. I R. BLIGH Em 2,401 604 MEANS FOR TUNING ELECTRICAL OSCILLATORS Filed Dec 23, 1945 2 Sheets-Sheet 2 Q. 2 A vc v 16 7 L CRYSTAL MULTi- FILTER FILTER- FILTER FILTER j osuumnwaamn O-l6 MC. MIXER IIIIIPI.IFII:R MIXER AMPLIFIER""AMELIIFIER 90 c. 90 KC. 61-8 Mo 0 so KC. 22-45mm IVY/V7 CRYSTAL MULTI- I 'rrmcxms VARIA'BLE TUNING FILTER j? osuLLA'ro .VIBRATOR ELEMENTS scILLA'Ton DEVICE "AMPLIFIER 90o KC. 900 KC. I 29 42' 0-23 KC. 1 4 I. I I 75 Receiver 30 F143 k 5 and Wansm/ffe? N 1221 J Low Frequei cy A.C. CRYSTAL I ATTORNEY Patented June 4, 1946 OSCILLATORS Norman Richard Bligh, Harrow, Douglas Max Heller, Wenibley Park, Luis Charles Stenning', Ealing, London, and Alexander Albert Chubby Shipley, England, assignors to The General Electric Company Limited, London, England Application December 23, 1943, Serial No. 515,401)

In Great Britain December 14, 1942 11 Claims. 1

This invention relates to apparatus for tuning a variable electrical oscillator and of the type comprising (a) an electrical generator or generators adapted to provide alternatively a set of standard frequencies spaced at minor intervals (say In), to one of whichthe variable oscillator has to be tuned-and a set of standard frequencies spacedat major intervals (say 10f (b) means for comparing the frequency f to which the variable oscillator is tuned with the frequency of any member of either of the said sets. As indi cated by the examples, the said intervals in any one set are preferably all equal in any one set and the major interval is preferably an integral multiple of th minor interval; both sets can then be harmonics of a single master oscillator and the second set derived from the first by suppressing members of it. But, though no advantage of departing from this arrangement is known, the equality of the interval in any one set and making the major interval an integral multiple of the minor are not essential to the invention. When the variable oscillator is said to be tuned to one of the standard frequencies of either of the said sets of standard. frequencies, it is not necessarily implied that it is made tooscillate at that frequency; it is implied only that it is made to oscillate at a frequency standing in some predetermined relation to (e. g. having an assigned difference from) that standard frequency. When the said relation obtains, the frequency of the variable oscillator will be said to coincide with that standard frequency.

In the use of means of this type it is possible to proceed as follows. The variable oscillator starts tuned to a frequency lower than the lower limit of the second set, and the said means (a) are made to giv the second set of frequencies spaced at major intervals. (Of course it would be equally possible to start beyond the upper limit.) 1 is increased until the said means (b) indicate that f coincides with a standard frequency, which must be the lowest member of the said second set. This fact is noted. f is increased furtheruntil it again coincides with a standard frequency, which must be the second of the said second set. The process is continued, the coincidences being counted, until 1 coincides with the member of the said second set next lowerthan the frequency to which the oscillator-is to be tuned.- (Alternatlvely it might be madeto coincide with the next higher member.) Means (a) are then made to give the first set of standard frequencies spaced at minor intervals. The process is then continued and the number of wind-- 2; dences with members of the first set counted, until there is coincidence with the desired member of the first set. The advantage of this procedure is, of course, that, when the member of the first set is large, fewer comparisons are necessary than if the oscillator were made to coincide in turn with each member of the first set below the desired frequency.

This method has been proposed in the specification of copending patentapplication Serial No. 484,332 filed April 24,, 1943; the present invention is specially adapted for use in association with the invention of that specification; its object is to enable the said procedure to be performed with ease and rapidity and, at least partly, automatically.

This object is achieved, according to one feature of the invention,. by providing driving means for varying continually in the same direction (at least so long. as the change-over means hereinafter mentioned do not operate) the frequency of the variable oscillator, by applying to an automatic selector switch, on the occasion of each coincidence between the frequency of the variable oscillator and a standard frequency, a pulse adapted normally to move its wiper on one step, by providing change-over means associated with the automatic selector switch for causing the second set of standardfrequencies to be replaced by the first set when the wiper reaches a predetermined stud of the automatic selector switch, means for varying at the will of the operator the number of steps that the wiper must take under control of said coincidences before it reaches the predetermined stud, and by providing also stopping means, adapted to be associated with differem steps of the" automatic select-Or switch, that put the said driving means out of operation when the wiper of the automatic selector switch reaches the stud with which the stopping means are asso- Alternatively, the change' 'o'ver means may be permanently associated With a predetermined stud of the automaticselector switch, means being provided: for varying at i the will of the operator the number of steps that the wiper must take under control of the coincidences before it reaches the predetermined stud.

' nd set. I

coincidences with this set, there must be m studs specification. Further, if the automatic selector switch is an instrument so equivalent, the terms wiper and. stud mean the elements of it cor-' responding in function to the wiper and stud of an instrument of the said kind.

Suppose then that the standard frequency to.

which the variable oscillator is to be tuned is such 4 of the automatic selector switch between (and including) the stud selected by the switch N2 and the stud a; this is secured by choosing suitably the position of the switch N2. a

After the stud Zia has been reached, coincidences occur with members of the first set of standard frequencies. The wiper therefore still moves on unitl it reaches a stud that has been selected by the switch NI. Then the drive of the motor ceases, a Signal lamp is lit; and a device is brought into operation which maintains f in coincidence with the desired member of the first set.

that the oscillator has to make 122 coincidences with the second set of standard frequencies and then an coincidences with the first set in order to V,

reach that standard frequency. change-over means might be associated with the 112 step of the automatic selector switch and'the stopping means with the (nz-i-m) step. But then the step with whichthestopping means would have to be associated would "depend on m as well as on n1. It is more convenient to make the position of the stopping means dependent only on m as the position of the change-over means is dependent only on m. The modifications of the simple arrangement thatare preferably made to produce this and some other subsidiary results are best explained by describing the general manner vof operation of a particular example of apparatus according to the invention.

In the accompanying drawings: Fig. l is a circuit diagram of the saidexample,

and

Fig. 2 is a block diagram of part of a radio transmitter-receiver station embodying the arrangement shown in Fig. l. r

Referring now to Fig. 1, the automatic selector switch, the wiper of which is denoted by W, has twenty-fiv studs, of which those numbered (Ea-29a are associated with a selector switch,N2 and the last five are associated with'a selector switch NI. On the shaft of the'wiper W are three cams 56, 5|, 52 in duplicate, of which'5l opens a contact 2025a only when the wiper is on one ofthe studs 29a to a and 52 close a contact 2l25a only when the wiper is on one of thestuds 2la to 25a;gthe function of the third cam 55 will be mentioned later. When the contact 2025a is open and the contact 2125a is closed, a relay'causes the generator of the standard frequencies to supply the first set of frequencies which (in this example) are 90 kc./s. apart; when the contact 2025a is closed and the contact 2|25a is open, the generator supplies the second set which (in this example) are 900 kc./s. apart. Accordingly the said contacts are the main part of the changeover means and the change-over is complete when the wiper reaches stud 2hr. I

When the start and change switches are operated, the wiper, starting at stud la, begins to move step by step, under the usual self -interrupting action of its driving magnet, until it reaches a stud selected by the selector switch N2. When it reaches that stud, it initiates actuation of a clutch, associated with a gear controlled by a relay, and causes a motor to drive the tuning element of the variable oscillator (not shown)- At the same time the magnet ceases to be supplied with pulses from its self-interruption and is sup-v plied instead with a pulse whenever a coincidence occurs between 1, the frequency of the variable oscillator, and a standard frequency of the sec- Consequently, ifthere' are to be m I Then the These constitute the aforesaid stopping means. For this purpose there must be m studs between (-andincluding) stud Zia and th stud selected by the switch NI; this again is secured by choos ing suitably the position of the switch NI.

That is the main operation; but some subsidiary operations are also important. First, it is desirable that the drive of the tuning element should 7 be slowed down when the wiper approaches the stud 20a just'before the change tothe. first set of frequencies occurs. This is conveniently achieved by providing a'second clutch associated with gear of a larger reduction ratio than the I like shall be understood, it is necessary to know something of the rest of the variableoscillator of which the devices shown in Fig. 1 form part. ,It' will be supposed that this generator is of the kind illustrated in Fig. 2, which is a modification of the drawings of copending application 'No. 484,332. The parts represented in the drawings of the copending application b numerals 31, 32 and 35 are irrelevant to this invention and have been omitted from the present Fig. 2. The parts represented by numerals 22-25, and 21-40 in the drawings of the copending applicationhave been profoundly modified; for the present invention is concerned with the substitution of automatic setting for. mere counting. The terminals 40, 4|, 42 and 43 of the present Fig. 1 are connected respectively to the terminals 40, 4|, 42 and 43 of present Fig. 2. g

Relays which are the same as the relays l9 and 20 of said copendingapplication and switches which are the same as the switches 6, 2| and 340i said copending' application play an important part in the following-description of the present invention. Of these the relays l9 and 29 and theswitch 2| are designated respectively by- Y, Z and RPZ, and are shown in Fig. 1 only. Switches 6 and 34 of said copending application are designated respectively MINI and O'II and are shown inboth Figs. 1, and 2 herein. However, the relaysv for operating these switches are shown only inFi g,'-1. The tuning. condenser'that forms part of the V tuning device 26 of Fig, 2 is n ot shown in Fig.1,

but the motor driving it is shown. W Thefilters l4, I5 of the present case are'modified from the filters l4, l5 of said co'pendingapplication in a manner to be explained later,-but --,the modification is immaterial so longas coincidences with standard frequencies of the second set-(major intervals) are being considered. For then,-whatever the nature of these filters, a co incidence occurs when the frequency of the variable oscillator comes within a range about the standard frequencies which is small compared with the interval between standard frequencies; it would make no diiierence if it were supposed that acoin'cid'ence was exact equality of'the frequency of the variable oscillator with ulster the standard. Accordingly consideration of these filters will be postponed until the account of setting to the second set of standards is complete.

- In Fig. 1 all relays and the like are shown in their un'operated condition. The convention adopted for showing the relays is that the energisin'g winding or windings of a relay are indicated by one or more rectangles which are interposed in the energisin'g, circuit or circuits and which are marked by a reference character consisting of a letter or letters denoting the relay. The contacts of the relay are shown underneath the rectangle and are denoted by serial numbers I, Z, 3, etc, so that a reference such as SA2 in the "specification denotes the number 2 contact of relay SA. The primary moving member in each relay contact is indicated by a plain arm without a contact head.

It will be assumed, that after the last use, the electric supplies were cut oif leaving the Wiper W in contact with some stud, other than Ia, which will be assumed to be different from that distinguished by the setting of NI or N2 switches shown, which will be assumed to be the required setting.

The nature of the parts shown in the drawings will generally appear best, in View of what has been said already, by a description of their function; but it should be stated that the operating magnet M moves the wiper on one step when it is released, "and that m is the self-interrupt contact that drives the wiper continually so long "as the necessary voltage is applied to it. The

symbols 1+3 attached to M refer to the one bank of studs (Ia-a) and the three contacts marked III, 2025a and 2I25a. The contact III is operated by 50, the third of the three cams associatedwith the wiper W as aforesaid, when and only when that wiper is at stud I a.

When the .start key is depressed, a contactor (not shown), which energises a motorgene'rator (not shown) supplying high-tension current to the associated apparatus, is closed. Simultaneously a 12 volt supply with earthed positive is connected between the bus-bars shown in Fig, 1.

The automatic selector switch magnet M is then energised via m'ake-before-break contact 'SCZ, the self-interrupting contact m, and the contact II I the wiper W is driven clockwise until it reaches the home position, when the wiper is resting on stud Ia and the contact III is opened.

Relay OT (which operates via contact R2) operates switch OTI and the tracking elements 33 ar "cut out. RP operates via th contact 2025a and DR operates via the cam 53 (which will be described later). RPI applies an earth to one side of the make-and-break contact YI via the contact 2025a. RPZ, DRI and DB2 assume the positions in which both filters Hand I5 feed relay Y'andoper'ate contact Y'I. FC 'is not operatedso that I 2P remains in circuit.

When the wiper has homed, S relay operates via the contact I I I, the contact CON, which is closed when the tuning condenser (forming part 6H6) r'eturnstoits starting 'po'sitionunder spring bias when the clutches are reieascagand 'th'ebbh tact CPN, which is open if the tuning condenser is driven by accident beyond its normal limit corresponding to the highest frequency required of the variable oscillator. S relay then self-holds via CPN contact and SI. SI also prepares to apply an earth to the contact arm of the NI selecting switch.- S2 applies an earth to one side of the magnet M, causing it to self-interrupt via m arid-SCZ. S3 applies an earth connection to the contact arm of'the N2 selecting switch which in turn earths 'a stud of the automatic selector switch corresponding to the N2 unit chosen. S4 prepares to sel fhold relays SA and SC and also applies an earth to one side of the tuning motor via SAI, which drives the tuning condenser, thus starting the motor.

The magnet M continues to self-interrupt until its wiper reaches the stud earthed via S3, when the SC relay is operated and locks itself operated via SCI and S4. The closing of SCI also operates the master clutc which establishes a connection with the tuning condenser via the fast clutch, so that the tuning condenser is driven at high speed. The magnet M remains operated, first through the upper contact of makebefore-break contact S03 and the wiper; after the said upper contact has opened, it remains operated via S02, SA2, YI, SAI, and S4, so that it will be released when YI breaks. Contact 504 applies an earth to the stud corresponding to the position of the NI selecting switch.

When the variable oscillator makes a coincidence with the first of the N2 series of standard frequencies, contact YI is opened momentarily by relay Y, releasing M and making the wiper take one step. This process continues on subsequent coincidences with the following members of the N2 set of standard frequencies until the wiper reaches stud 28, when eontact2025a opens. Relay RP does not relax immediately the coincidence occurs that causes the wiper to move to stud 20a; for it is self-held by contact RPI. It is released only when the coincidence ceases, i. e. when f passes beyond the range about the standard of the second set within which contact YI is operated. (The importance of this will appear presently.) When the coincidence ceases, the circuit of RP is broken and the RP contacts are operated. R'P2 separates the pulses delivered by the rectifiers I! and f8, and applies them separately to relays Y and Z. RP3 substitutes the medium for the fast clutch and therefore causes the tuning condenser to be driven more .slowly as coincidence with the last of the standard frequencies of the second set is approached. When contact YI is operated by this approach, the wiper is stepped to stud [Ia and the contact 2 I251 closes. Relay MIN is operated and changes over switch MINI, thereby substituting the first set of standard frequencies (minor intervals) for the second set. Subsequent coincide'nces will be with members of the first set;

the row positions e. g. A, B, C and D) in NI -operate Z or vice versa.

applied to the two filters. One of these passes frequencies between (or substantially 0) and a limit slightly greater than /4fo, where f0 is the difference between successive standard frequencies; the otherpasses frequencies between /2fo and a limit slightly less than f0. Thus in the present example, where fo=90 kc., the said limits may be 23 and 22 kc. respectively. If oscillations passing the first said filter cause the frequency of the variable oscillator to decrease and oscillations passing the second said filter cause it to increase, then the frequency of the oscillator will 'tend'towardsa value /410 less than the standard frequency, at which both sets of beats pass their filters owing to the overlap of these filters. It can be arranged that within this overlap neither set of beats causes the frequency of the oscillator tovary, sothat this frequency will remain very near thesaid value. If the functions of the two sets of beats are interchanged, i. e. if those passing' the first filter increase the frequency and those passing the second filter decrease it, then the frequencyv of the oscillator will remain very near a value Afo greater than the standard frequency.

-. The filter 14 has then a pass range /gfo to just less than /0 (say, if f=90 kc., 45-22 kc.), and filter a pass range from just more than /4fo to substantially zero (say 23-02 kc.). The said interchange of the functions of the two sets of beats is effected by the contacts DRI, DRZ, of relay DR which causes M to operate Y and IE to The relay DR is operated by a first cam 53 on the shaft of the contact arm of selector Ni when that arm passes from the first to the second pair of contacts connected to the same wiper stud, e. g. from (A, B)

to (C, D.) or from (E, F) to (G, H). The passage from the first contact to the second contact of such a pair operates contacts via a second cam 54 on the shaft of the contact arm of Ni which operate a relay FC whose contact FCI (Fig. 1) substitutes (as suggested in the said specification -No. 484,332) for one crystal oscillator .IZP another I2Q oscillating at a frequency /410 higher. It thus effectively raises the whole series of standard frequencies by /4Jo.

'Suppose then the arm of N I is on contact A. Then the variable oscillator will set itself (by means about to be described to njo- Aft, where M0 is one of the first set of standard frequencies.

.When the arm changes to B, IZQ is substituted for I 2? and the oscillator sets itself to nfo; when the arm moves to 0, HP is replaced, but now the oscillator sets itself to nfo+%fa, in virtue of the changeover of the switchesDRl, DRZ. When the arm reaches D, the oscillator sets itself to nfo+ /2fo. When the arm reaches E, the oscillator sets itself to (n+l)fo'%,-fo=nfo+%fo.

-The result isthat the effective minor interval is not forbut /l fo.

The operationof the main device will now be 'A coincidence, operating possibly by the substitution of I2Q for IZP; the coincidence ceases and the magnet is released when reaches a value %f0 higher. It is now clear why it is important that RP should not operate and throw over RPZ before the magnet is released; for if it did, the magnet would be released beforethe penultimate standard of the second set was reached and would be energised again soon after that standard was passed; there 75 action of contact Yl, until the stud selected by N I is reached. Then relay SA is operated through contact SC3, whichis still operated,

Relay SA locks itself in the operated via SA5 and S4. Contact 8A4 de-energises both the fast and medium clutches, and prepares to operate relay ME via contact YI or ZI, when either of the make-and-break these contacts is operated. Contact SA3 removes the -12. volt supply from one side of the tuning motor and substitutes a connection to the movingv member of contact ZL. Contact SAI, removes the earth connection from the other side of the tuning motor, leaving it connected to the moving member of contact Yl. operated both sides of the motor are joined to the 12 volt supply and the motor does not run and ME is unoperated. Similarly, when both Zl and YI are relaxed the two sidesof the motor are connected to earth (direct and via SA2 respectively) and again the motor does not run and ME is unoperated. However, if 2! is operated and Yl relaxed the motor is driven in a forward direction, 1. e. in the same direction as during the counting operation. Conversely, if Zl. is relaxed and Yl is operated, the motor is driven in the reverse direction, ME being operatedineither case. i

The slow clutch relay is energised through contact MEZ in parallel with SA and causes the tuning condenser to be driven very slowly either forwards or backwards according as Zl or Yl is operated; ,f is thus automatically maintained in the desired relation with the selected standard. Contact MEI, being open, prevents the operation of relay R until the motor is de-energised for the first time, whereuponR operates and locks itself operated via RI, SAI and S4. The ready lamp also lights, being effectively in parallel with R relay. The make-and-break contact R2, being operated, removes the earth from the relay OT and puts the tracking elements 33 in circuit; the control of switch OTI by energisationrof relay OT, and hence the removal or insertion of the tracking elements, is transferred to the pushto-transmit key. Contact R3 prepares to operate relay TD on depression of that key.

The apparatu now is in the state for the reception of signals. the push-to-transmit key is depressed and the tracking elements are cut out by the operation of relay OT. The contacts of the ,relay TD and the contacts of the relays MIN and OT not explicitly mentioned perform certain operations incidental to transmission or reception, (e. g. the

again. This it does mainly by releasing the relay W S and therefore causing all S contacts to return to the unoperated state. Experts will understand position When both Yl and Zl are If signals are to be transmitted,

has to be tuned, and a second set of standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for ap-' plying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, and stopping means adapted to be associated at the will of the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated.

2. Apparatus of the character described for tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction thefrequency'of said oscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator between the varying frequency of said variable oscillator and said standard frequencies for applying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means permanently associated with a predetermined stud of said automaticselectorswitch for causing said second set ofstandard frequencies to be replaced by said first set when the wiper reaches said predetermined stud, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, and stopping means adapted to be associated at the will of the operator with different studs of said automatic selector switch and servingto put said driving means out of action when the wiper reaches the stud with which said stopping means are associated.

4. Apparatus of the. character described for tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequencyof said oscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set of standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for ap plying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means including a selector switch for selecting a prehas to be tuned, and a second set of standard set of standard frequencies to be replaced by said first set when the wiper reaches the stud with which said change-over means are associated,

and stopping means also adapted to be associated at the will of the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated.

3. Apparatus of the character described for tuning'a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequency of said loscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to lie-tuned, and a second set of standard frequencie'sspaced at major intervals, an auto- "matic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, 'means responsive to coincidences determined stud of said automatic selector switch, a source of current, a relay and a circuit including-sa ldrelay in series with said source of current and with saidselector switch and capable of being completed by the wipers reaching said predetermined stud'and thereby causing said second set of standard frequencies to be replaced by said first set'when the wiper reaches said predeter-- mined stud, and stopping means adapted to be associated at the will'of the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the .wiper reaches the stud with which said stopping means are associated.

5. Apparatus of the character described for tuning a variable electrical oscillator and including driving'means capable of varying continuously in the same direction the frequency of said oscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set of standard frequencies spaced at major intervals, an automaticselector switch including a wiper, a plurality o-f studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for applying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set when the wiper reaches a predetermined stud of said automatic selector switchJmeans for varying at the will of an operator the number of steps that said wiper must'take under control of said coincidences stopping means including a selector switch for selecting a second predetermined stud of said automatic selector switch, a source of current, a relay and a circuit including said relay in series with said source of current and with said selector switch and capable of being completed by the wipers reaching said second predetermined stud.

6. Apparatus of the character described for tuning a variable electrical oscillator and includingdriving means capable of varying continuously in the same direction the frequency of said oscillator, mean for changing the effective speed of said driving means, means forgenerating alternatively a first set of standard frequencies spaced at minor intervals, to oneof which the variable oscillator has to be tuned, and a second set of standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a pluralityof studsand electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard, frequencies for applying to said automatic selector switch, on the, occasion of each such coincidence, a pulse serving to move its wiper one step, change? over means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set and for actuating said means for changing the effective speed of said driving means so as to cause the frequency of said variable oscillator to vary more slowly when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, and stopping means adapted to be associated at the will of the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated.

7 Apparatus of the character described for tuning a variable electrical oscillator, includin a control member capable on continued displacement in the same direction of varying continuously in the same sense the frequency of said oscillator, a motor, a'two-speed gear mechanism connecting said motor to said control member and including electrically-actuated gear-selecting clutch means, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set of standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for applying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set and for actuating said clutch means so as to cause the frequency of said variable oscillator to vary more slowly, when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, and stopping means adapted to be associated at-the will of the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated;

' 8. Apparatus of the character described for tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequency of said oscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set of standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a pmrality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequenciesfor applying to said automatic selector switch, on the occasion of each such coincidence, a pulse'serving to move its wiper one step, change-over means associatedwith said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, stop- 4 tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequency of said oscillator, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set of standard frequencie spaced at major intervals, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for .applying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, change-over means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predeterminedstud, stopping means adapted to be associated atthe will of the operator with diflerent studs ofsaid automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated, and means for maintaining the frequency of said variable oscillator in a predetermined relation to a selected standard frequency after it has beenbrought, at least approximately, into such relation, the last-mentioned means including two filters, one passing frequencies only between substantially zero and a limit slightly exceeding 12], where I is the effective difference between successive standard frequencies of said first set, in the absence of the lastmentioned means, and the other filter passing frequencies only between fo and a limit slightly less than %f0, and two relays arranged to be actuated in response to passage of current through said filters respectively and to cause said driving means to operate in the one or the other direction according as only one or other of said relay is actuated.

10. Apparatus of the character described for tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequency of said oscillator, means for changing the effective speed of said driving means, means for generating alternatively a first set of standard frequencies spaced at minor intervals, to one of which the variable oscillator has to be tuned, and a second set f standard frequencies spaced at major intervals, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to coincidences between the varying frequency of said variable oscillator and said standard frequencies for applying to said automatic selector switch, on the occasion of each such coincidence, a pulse serving to move its wiper one step, changeover means associated with said automatic selector switch for causing said second set of standard frequencies to be replaced by said first set and for actuating said means for changing the efiective speed of said driving means so as to cause the frequency of said variable oscillator to vary more slowly when the wiper reaches a predetermined stud of said automatic selector switch, means for varying at the will of an operator the number of steps that said wiper must take under control of said coincidences before it reaches said predetermined stud, stopping means adapted to be associated at the Will of'the operator with different studs of said automatic selector switch and serving to put said driving means out of action when the wiper reaches the stud with which said stopping means are associated, and means for maintaining the frequency of said variable oscillator in a predetermined relation to a selected standard frequency after it has been brought, at least approximately, into such relation, the last-mentioned means serving to control said driving means in such a manner that the frequency of said variable oscillator is varied for the purpose of maintaining said frequency more slowly than just after said change-over :means have operated.

11. Apparatus of the character described for tuning a variable electrical oscillator and including driving means capable of varying continuously in the same direction the frequency of said oscillator, a first generator of a set of standard frequencies spaced at uniform intervals in, a second generator adapted in two alternative conditions to generate respectively two frequencies differing from each other by IAJO, means for mixing the outputs of said variable oscillator and of said first and second generators, two filters for receiving such mixed output, one passing frequencies only between substantially zero and a limit slightly exceeding ,)0, and the other passing frequencies only between /2fo and a limit slightly less than Ado, an automatic selector switch including a wiper, a plurality of studs and electrically actuable wiper moving means, means responsive to the passage of a current pulse through at least one of said filters for applying to said automatic selector switch a pulse serving to move its wiper one step, a selector switch for selecting a predetermined stud of said automatic selector switch, said selector switch having four positions associated with each stud of said automatic selector switch, stopping means serving at least momentarily to put said driving means out of action when the wiper reaches the selected stud, two relays arranged to be actuated in response to passage of current through said filters respectively and to cause said driving means to operate in the one or the other direction according as only one or other of said relays is actuated, and means actuated by said selector switch for interchanging the functions of said filters as said selector switch changes from the first pair to the second pair of said four positions and for changing the condition of said second generator as said selector switch passes from the first to the second of each of said pairs of positions.

NORMAN RICHARD BLIGH. DOUGLAS MAX HELLER. LUIS CHARLES STENNING. ALEXANDER ALBERT CHUBB. 

